Hornbills are synonymous with Sarawak. In fact, Sarawak is home to eight of the 62 hornbill species that exist worldwide, including the iconic Rhinoceros Hornbill, also called Kenyalang by the Iban. However, how accurately can Sarawakians name or classify the eight hornbill species?
How well do you know your hornbills?
This is the first of a three-part series on Hornbills in Sarawak article.
Apart from being known as the Land of the Hornbills, Sarawak’s state crest is also represented by a wing-spread Rhinoceros Hornbill with a shield bearing the state flag on its chest.
Hornbills, known as “Burung Enggang” in Bahasa Melayu, play an important role in the culture of many communities in Sarawak, carrying several different meanings to the respective indigenous communities. They are deeply associated with the local culture and are a common subject in legends, traditional ceremonies, and beliefs.
According to the beliefs of the Iban people, “Kenyalang”, which is refers to the iconic Rhinoceros Hornbill, represents their god of war, Sengalang Burong.
How precisely can Sarawakians identify the eight hornbill species, though?
From a brief observation I made after reading several posts on social media regarding hornbills, many locals continue to mix hornbills with Kenyalang. Most social media users believe that all hornbill species in Sarawak go by the name Kenyalang.
In addition, several roadside billboards and social media pages frequently feature the incorrect hornbill species to represent our state. Many times, the Great Hornbill, which can only be found in West Malaysia, was employed instead of the Rhinoceros Hornbill that was intended to be used.
A master’s research project carried out by the Wildlife and Habitat Conservation Officer of WWF-Malaysia, Philovenny Pengiran, at Universiti Malaysia Sarawak (UNIMAS), in collaboration with Sarawak Forestry Corporation (SFC), backed up my observation.
She claimed that the majority of her respondents used Kenyalang to describe all of the hornbill species in Sarawak, with the exception of a few who responded with Burung Sarawak, which is translated as Sarawak bird, given the significance of the state’s coat of arms.
Morphology and ecology
According to SFC, based on the classification of living organisms, hornbills are classified in the order Bucerotiformes and split into two families, namely Bucorvidae and Bucerotidae. Both families are distinguished based on their anatomy, including casque and beak shape, behaviour, development, and how closely they are related.
Hornbills have a large beak and have their own characteristics. This bird gets its name from its horn-like bill. Its large and curved beak makes the hornbill look very attractive.
Hornbills also have an additional structure on top of their beak called a casque. The casque is made of keratin, which is a structural protein found in human hair, nails, and skin. Most casques are hollow and function as resonators for calls. The Helmeted Hornbill, however, has a more solid casque.
Hornbills are large birds with a body length of 65 to 170 centimetres and a weight of 290 to 4,200 grammes. Males have brighter plumage and larger bodies than females. Their bodies are almost entirely covered by feathers of various collars: black, grey, white, or other colours (yellow and red) on their necks, heads, and around the eyes.
Adult hornbills are sexually dimorphic and can be distinguished by the colour of their casques, wings, beaks, eyes, and body size. In addition to their morphology, hornbills can be identified by their calls and wing flaps.
According to Amin and Ripot (2017), these birds live in monogamous pairs (with one male and one female) and occupy about 1.2 square kilometre square (km²) to 2.3 km² of forest area per pair. They generally require an intact primary forest that provides suitable nest sites (natural cavities) and sufficient food resources.
There are 62 species of hornbills in the world, 10 of which are found in Malaysia. However, only eight of the 10 species can be found in Borneo; the Great Hornbill (Buceros bicornis) and Plain-pouched Hornbill (Rhyticeros subruficollis) are the exceptions.
The occurrence of hornbills in the forest indicates the presence of large trees in the area. On the other hand, the hornbill population is closely linked to a healthy forest because hornbills need diverse fruit trees for feeding and large trees with cavities for nesting. In other words, protecting the hornbills means protecting the forest and the carbon stored within.
All species of hornbills have diverse habitats, from mangrove forests to hill forests. There is also a species of hornbill that is widespread and easily adapted to human habitats, namely the Oriental Pied Hornbill.
Hornbills also play an important role in forest ecology. They are known as farmers of the forest because of their role in spreading fruit tree seeds. The seeds are dispersed through regurgitation or defecation, as the birds’ digestive systems leave the seeds intact and help forests regenerate.
Hornbills can be found in most national parks, including Gunong Mulu National Park, Tanjung Datu National Park, Batang Ai National Park, Similajau National Park, and Piasau Nature Reserve. However, it is impossible to predict when one will be able to observe the birds.
To meet their nutritional requirements, these enigmatic birds usually eat fruits or are mostly frugivores. During breeding season or low fruit season, hornbills will eat other prey or behave more omnivorously. The hornbill’s large, curved beak is an adaptation of its diet.
The fruits that make up their diet and are collected from trees and not the ground are grouped into three types: drupaceous or fleshy fruits containing fats, husked fruits, and figs with high water, carbohydrate, protein, and calcium content. Hornbills also eat fruits that contain sap during breeding season as nest-sealing material.
Other sources of food, including insects, reptiles, crabs, small mammals, and small birds, are important for the hornbill’s physical growth and physiological development, especially during egg development.
There are several ways that hornbills obtain their food, such as levering, digging, chasing, swooping, plucking, and hawking. Before ingesting, hornbills will crush, soften, carry, or swallow. All these may be done at the same time, depending on the type of food.
There are two ways that hornbills consume fruits. The first is by picking up and softening the fruit in their beaks and then regurgitating the seed after the rest of the fruit has been ingested. The second method is by swallowing the fruit (which generally has small or fine seeds) through their beaks and into their throats before entering their digestive system. The seeds are then defecated on by the birds.
In the wild, hornbills depend entirely on forest conditions, and they have unique nesting habits. They do not make their own nest and rely entirely on hollows, whether broken-off trunks or the abandoned nests of other animals, followed by a weathering process, as nesting sites.
They nest in holes or hollows in large trees that are at least 45cm in diameter.
Before the breeding season arrives, a pair of hornbills will visit several hollows before deciding which one is suitable for nesting.
Due to the high level of destruction of trees and tree hollows, the number of adequate hollows is limited. Therefore, an ideal nest cavity may be used repeatedly by the same or different species.
During incubation, the female hornbill seals herself inside the tree cavity. Its entrance is sealed by a plaster of dirt, mud, bits of food, and droppings to protect her egg from predators and threats from outside of the nest. Only a small slit remains to allow her mate or other group members to pass through food and discard droppings.
The female then sheds its feathers to incubate the eggs. A number of hornbill species molts at the start of the incubation process, and these feathers will regrow when the female leaves the nest.
The incubation period varies among hornbill species. For small hornbills, incubation is 25 days but may take up to 150 days for larger species.
For example, the Wreathed Hornbill incubates its eggs for 40 days, the Rhinoceros Hornbill takes 37 to 46 days, and the Helmeted Hornbill takes the longest with 150 days. These differences may be influenced by regional variations.
Overview of hornbill distribution and abundance in Sarawak
According to the Malaysian Nature Society (MNS), hornbills were detected at 119 sites in the 12 different divisions of Sarawak. The species that occurred at most of the sites was the Black Hornbill (65 sites), followed by the Rhinoceros Hornbill (54 sites) and the Bushy-crested Hornbill (54 sites).
Out of all the hornbill species, Wrinkled Hornbill has the fewest sightings recorded in Sarawak (15 sites). According to BirdLife International (2021), the Wrinkled Hornbill is currently classified as Endangered.
Based on the findings, the MNS team suspects that the Wrinkled Hornbill in the state might be critically endangered due to its low tolerance for habitat change and the rapid destruction of its remaining peat swamp habitat in Malaysia. As peat swamp forests slowly disappear, it becomes difficult to see the birds.
Helmeted Hornbills were detected in several sites and divisions but are not presented in the study due to a possible poaching threat to this species.
Meanwhile, eight species of hornbills were recorded in five divisions, namely Bintulu, Kapit, Kuching, Limbang, and Miri; seven species in Sibu and Sri Aman; four species in Betong and Mukah; three species in Samarahan and Serian; and one species in Sarikei.
Apart from that, a total of 5,460 hornbill individuals were recorded. Few hornbill individuals were recorded before the year 1992, with the exception of 1972 to 1981. There was a spike in hornbill records from 1972 to 1981 because Kemp & Kemp (1974) conducted research in the state in 1974, which accounted for 638 out of the 663 hornbill individuals recorded in that decade.
Overall, with 85 per cent hornbill records in the assessment observed after the year 2000, one may mistakenly assume that the hornbill population is growing at a rapid rate in Sarawak. However, this is more likely due to the availability of better-quality cameras and Internet or social media platforms for birders to share their records easily and publicly on websites like ebird.org in recent decades.
Before such technology was available, hornbill sightings were recorded in diaries, personal bird lists, and others, which are more difficult to access. Sarawak’s population has also increased over the past few decades. This has resulted in an increase in observers (birders and researchers) in Sarawak, which may have resulted in an increase in the number of hornbill records in recent decades.
Thus, the increase in hornbills recorded over time is likely not a real increase in hornbill populations but due to better technology and an increased number of observers. On the contrary, hornbill populations have declined due to declining forest habitat.
